A. Field of the Invention
The present invention relates to the field of image display systems, and, in particular, user interfaces for the display and operation of large-scale informational sources, such as hypertext, three-dimensional books, databases, and other repositories of information.
B. Description of the Prior Art
The ability of users to access and interact with information in electronic form (i.e., the reading of, manipulation of, and navigation through data) gains ever-increasing importance as the volume of accessible information increases. Electronic information is generally stored in the form of documents that are displayed to the user upon request. Users or readers of information must accustom themselves to the controls for accessing and interacting with the electronic information.
The documents accessed by a user may include documents created by a user via a text-editing computer program such as a word processor. In addition, documents may also be scanned into a computer resulting in an electronic version of a paper document. The scanning operation may include the optical character recognition of the document so that both the graphical information (digitized images of the pages) and contextual information (a text file of the document) from the document may be stored together or otherwise linked. Electronic documents are also widely available over the Internet via the World Wide Web, among other electronic document sources. Documents may then be displayed with a display system, such as with a computer having a monitor, or other similar display devices, for example.
A typical method of displaying an electronic document is to represent the document as a continuous scroll with an associated scroll-bar for advancing the displayed representation. Most word processing programs and Web browsers utilize this scroll metaphor for displaying electronic information. The display of electronic documents as a continuous scroll, in the conventional manner, may possess a number of deficiencies in displaying certain types of documents. For example, users may have difficulty accessing and interacting with information when a conventional scroll is applied to a large document.
Another metaphor for displaying electronic information is that of a three-dimensional book. U.S. Pat. Nos. 5,838,326 and 5,847,709 to Card et al., which are expressly incorporated herein by reference, disclose a program for displaying a document workspace for interacting with electronic documents in the form of three-dimensional books. The purpose of the document workspace is to allow a large number of document objects to be displayed together (mitigating the limitations of the small screen space) in order to support information-intensive activities. Interaction with pages is similar to the functionality of a World Wide Web browser. The design aims to provide very rapid access to a small number of pages, smoothly integrated with slower access to a large number.
An exemplary document workspace is illustrated with reference to FIG. 1. The document workspace is arranged hierarchically, based on interaction rates, into three main levels: a Focus Space (for the document objects in active use), Immediate Memory Space (for document objects in use), and Tertiary Space (for document objects not in use). In FIG. 1, a document object 5 is in the focus space. The immediate memory space comprises a “desk” 10 and an area behind the focus space. The desk 10 may also contain document objects, e.g., document object 15.
The tertiary space is where document objects may be positioned when they are not in use. For example, document objects that are used for reference purposes are placed in the tertiary space. Referring to FIG. 1, the tertiary space is represented as a bookcase 20. Bookcase 20 includes document objects 30 and 35, for example.
If the user “touches” one of documents in bookcase 20, it will automatically “fly” to the focus space. Simultaneously, any document object then in the focus space will fly to a position in the immediate space. The “flying” of objects is an animation which shows the movement of objects from one space to another. The user is thus able to access information from the plurality of displayed document objects by bringing the document into the focus space. The user may manipulate the positioning and view of the documents through any known method, for example, via a drag and drop operation.
As used herein, a document object is any entity that can be manipulated in a document workspace. A document object contains two basic types of information: content information and display/manipulation information. The content information refers to the text and image data for the underlying document. The display/manipulation information refers to data defining how the text and image data is to be presented to the user.
Known systems have been relatively successful in displaying books having a small number of pages. However, the display of larger books containing hundreds of pages or more poses challenges in how to interact with these large documents.